JPH03199954A - Pure-water sensor - Google Patents

Abstract

PURPOSE:To make it possible to sense pure water in a short time by arranging a porous ethylene tetrafluoride resin material containing a conductive material and surface-active agent at a part between electrodes. CONSTITUTION:In this sensor 6a, a porous ethylene tetrafluoride resin material containing a conductive material and a surface-active agent separates electrodes 4a and 5a. A protecting layer 7a of an insulator is provided around the sensor. The sensor 6a is always dry. The electric resistance of the material 3a is adjusted with the rate of content of the conductive material and set at a relatively low value. The resistance is initially measured with a resistance measuring device through lead wires 8a and 9a. When pure water which is an insulator comes into contact with the part of the material 3a, the surface tension of the sensor 6a is decreased with the surface-active agent. The pure water intrudes into the inside, and the electric resistance of the material 3a is increased. The resistance is measured with the resistance measuring device and compared with the initial measurement. Thus the presence of the pure water can be detected in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a pure water detection sensor suitable for cases where pure water, which is an insulator, leaks.

[Prior Art] Conventionally, a fluid sensing element (characterized in that at least two electrodes are isolated by disposing a porous tetrafluoroethylene resin material containing a conductive substance in a portion between the electrodes) has been proposed.
(see Japanese Patent Publication No. 59-47256) is publicly known.

This is because porous tetrafluoroethylene resin, which contains a relatively large amount of conductive substances such as carbon particles, has a conductive mechanism based on a two-dimensional chain of carbon particles, but if there is an oil leak, Detection is performed by utilizing the fact that oil infiltrates between conductive substances (inside the resin), inhibits conductivity due to the tunnel effect, and rapidly increases the electrical resistance value of the resin.

[Problems to be Solved by the Invention] However, the critical surface tension of the porous tetrafluoroethylene resin used in this fluid sensing element is smaller than that of water and larger than that of oil. It has the function of absorbing particles, but it easily releases moisture, so
Pure water, which is an insulating liquid but has a high surface tension, cannot penetrate into porous tetrafluoroethylene resin materials that contain conductive substances, or it takes a very long time to penetrate, so it is practically impossible to detect. There was a problem.

Nowadays, there is a lot of ultrapure water that is extremely free of impurities and is used for cleaning electronic parts, circuit boards, etc., so there is an increasing demand for sensors that can detect this pure water in a short time.

The present invention was developed in view of the above-mentioned demands and to solve these demands, and it is an object of the present invention to provide a pure water detection sensor capable of detecting pure water in a short time.

[Means for Solving the Problems] The present invention has been made to achieve the above problems, and includes disposing a porous tetrafluoroethylene resin material containing a conductive substance and a surfactant in a portion between the electrodes. This constitutes a pure water detection sensor characterized in that at least two electrodes are isolated.

[Function] According to the present invention, at least the electrodes are isolated by disposing a porous tetrafluoroethylene resin material containing a conductive substance and a surfactant in a portion between the electrodes. Configure a pure water detection sensor.

Here, the conductive substance used in the present invention is a powdery substance having conductivity, such as graphite powder, carbon black powder, carbon fiber, various metal powders (powders of platinum, gold, silver, titanium, tantalum, etc.), and cermet. (titanium carbide, chromium, etc.), metal nitrides (titanium nitride, aluminum nitride, etc.), metal borides (titanium boride, zirconium boride, etc.), metal silicides (molybdenum silicide, etc.), Oxide (Cu, 01TiO1V
Examples include oxides such as O, Mn OS CO01NiO1ZnO, CaO, etc., which are given conductivity by making the ratio of oxygen non-stoichiometric), metal raw electrodes, organic raw electrodes, etc.

Further, the surfactant used in the present invention includes a solid surfactant such as soap powder, and a liquid surfactant prepared by dissolving it in pure water or the like.

An example of how to make the pure water detection sensor of the present invention will be explained.

First, the above-mentioned conductive substance powder is mixed with tetrafluoroethylene resin powder at a certain ratio, and through steps such as stirring, extrusion, and rolling, a porous tetrafluoroethylene resin having electrical conductivity is obtained. In this case, since a certain degree of elasticity is required in each step, the proportion of the conductive substance in the porous tetrafluoroethylene resin is usually 5 to 70% by weight, preferably 10 to 50% by weight. In addition, for example, colored pigments and fluororubber for maintaining strength may also be added.

Further, for example, as described in Japanese Patent Publication No. 48-44664 and Japanese Patent Publication No. 51-18991 (1), unfired porous tetrafluoroethylene resin is stretched in one direction by about 1 to 15 times. Materials with increased porosity or materials that are incompletely fired are suitable for the present invention because they allow liquid to penetrate more easily. Note that the incomplete firing also includes the purpose of increasing dimensional stability.

Next, separate electrodes are connected to both ends of this conductive porous tetrafluoroethylene resin, creating a type of resistance element.

Next, the electrically conductive porous tetrafluoroethylene resin of this resistance element is soaked in a liquid surfactant such as soapy water using pure water. Since this liquid surfactant has a low surface tension, it can penetrate into the porous tetrafluoroethylene resin relatively easily. Furthermore, if it takes a long time to wait for natural infiltration, the liquid surfactant may be forced to infiltrate into the porous tetrafluoroethylene resin by applying pressure or the like.

Finally, the whole is dried and returned to a solid surfactant while remaining dispersed in the porous tetrafluoroethylene resin.

Another method is to mix the solid surfactant powder with the tetrafluoroethylene resin powder at the same time as the conductive material powder. However, in that case, a solid surfactant powder must be selected that does not interfere with the subsequent steps.

When the pair of electrodes of this pure water detection sensor is connected to a resistance measuring device, the electrical resistance of the conductive porous tetrafluoroethylene resin remains relatively low, but the pure water, which is an insulator, becomes conductive. When it comes into contact with porous tetrafluoroethylene resin, the surface tension of pure water is lowered by the surfactant and it easily penetrates into the interior, and as a result, the pure water, which is an insulator, forms porous tetrafluoroethylene resin, which has electrical conductivity. Since the electrical resistance value of ethylene resin increases significantly, the presence of pure water can be detected in a short time.

[Embodiment] Figure 1 is a plan view of a pure water detection sensor showing an embodiment of the present invention. Further, FIG. 2 is a sectional view taken along line AA' of the pure water detection sensor shown in FIG.

To explain based on FIG. 1 and FIG. 2, pure water is characterized in that a porous tetrafluoroethylene resin material 3a containing a conductive substance and a surfactant is separated by an electrode 4a and an electrode 5a. A detection sensor 6a is shown.

just! 7. Pure water detection sensor 6 shown in Figures 1 and 2
When a is completely exposed, a porous tetrafluoroethylene resin material 3a containing a conductive substance and a surfactant,
If the electrodes 4a and 5a are grounded, it may be difficult to detect the water effectively or there is a risk that the pure water detection sensor 6a itself may be destroyed, so a protective layer 7a of an insulator is placed around the pure water detection sensor 6a. It is set up.

Note that this protective layer 7a may be an insulator and have a structure that allows pure water, which is the liquid to be measured, to reach the pure water detection sensor 6a, so for example, a through hole may be provided in the protective layer 7a, or This can be achieved by using a porous tetrafluoroethylene resin material containing a surfactant for the protective layer 7a.

Further, lead wires 8a are connected to the electrodes 4a and 5a, respectively.
and the lead wire 9a are connected by pressure welding or the like.

This pure water detection sensor 6a is always dry, but at that time the electrical resistance of the porous tetrafluoroethylene street resin material 3a containing a conductive substance and a surfactant between the two electrodes 4a and 5a is Although the electrical resistance is adjusted by the content of the conductive substance, it is set at a relatively low electrical resistance. An initial measurement is performed using a resistance measuring device (not shown) using lead wire 8a and lead wire 9=+.

Here, when pure water, which is an insulator, comes into contact with a portion of the porous tetrafluoroethylene resin material 3a containing a conductive substance and a surfactant, the surface tension of the sensor may be lowered by the surfactant 2a. As a result, the electrical resistance value of the porous tetrafluoroethylene resin material 3a containing a conductive substance and a surfactant increases significantly. This is measured by a resistance measuring device (not shown), and then By comparing with any initial measurement, the presence of pure water can be detected in a short time.

Further, the resistance measuring device (not shown) may be freely linked to, for example, an alarm buzzer or an alarm lamp (not shown).

FIG. 3 is a perspective view of an end portion of a pure water detection sensor showing a different embodiment of the present invention.

To explain based on FIG. 3, by disposing a porous tetrafluoroethylene resin material 3b containing a conductive substance and a surfactant between the electrodes, the electrodes 4b and 5b
A pure water detection sensor 6b is shown, which is characterized by isolated water.

Note that a protective layer 7b made of an insulator and having through holes through which pure water can pass is provided as necessary on the outside of the electrode 5b. Moreover, this protective layer 7b can also be formed using a porous tetrafluoroethylene resin material containing a surfactant.

The structure of the pure water detection sensor 6b is a coaxial cable type pure water detection sensor 6b in which the electrode 4b is the center conductor and the electrode 5b is the outer conductor such as a braided conductor. It has the characteristic that it can be installed in

FIG. 4 is a plan view of a pure water detection sensor showing still another embodiment of the present invention. Moreover, FIG. 5 is a sectional view taken along line cc' of the pure water detection sensor shown in FIG.

Based on FIG. 4 and FIG. 5, the electrodes 4c are
This shows a pure water detection sensor 6c characterized in that the electrode 5c is isolated from the electrode 5c.

Note that a protective layer 7c made of an insulator is provided outside the pure water detection sensor 6c, if necessary, and has through-holes etc. through which pure water can pass.
We have set up. Moreover, this protective layer 7c can also be formed using a porous tetrafluoroethylene resin material containing a surfactant.

Further, lead wires 8c are connected to the electrodes 4c and 5c, respectively.
and the lead wire 9c are connected by soldering or other methods. In addition, the entire structure is supported by a plate TOc.

Since the pure water detection sensor 6c has the electrodes 4c and 5c arranged in a comb shape, it is suitable for a relatively wide area.

[Effects of the Invention] As explained above, according to the present invention, at least two electrodes can be connected by disposing a porous tetrafluoroethylene resin material containing a conductive substance and a surfactant in a portion between the electrodes. Since the pure water detection sensor is characterized in that the surfactant is isolated, the surface tension of the pure water is lowered by the surfactant, so that the pure water can be detected in a short time.

It should be noted that the present invention is not limited to the above embodiments, and for example, it may be possible to use a surfactant other than soap, or to extend reinforcing wires to maintain the shape even though it is deformed into various shapes. The present invention can be implemented by molding the connecting part between the electrode and the lead wire using resin or the like, or by connecting another resistor between the conductive porous tetrafluoroethylene resin material and at least two electrodes. Of course, various changes are possible within the technical philosophy.

[Brief explanation of drawings]

Fig. 1 is a plan view of a pure water detection sensor showing an embodiment of the present invention, and Fig. 2 is a plan view of the pure water detection sensor shown in Fig. 1.
A' sectional view, the third figure is a perspective view of the end of a pure water detection sensor showing a different embodiment according to the present invention, and the fourth figure is a plan view of a pure water detection sensor showing a further different embodiment according to the present invention.
FIG. 5 is a cross-sectional view taken along line cc' of the pure water detection sensor shown in FIG. 3a, 3b, 3c: porous tetrafluoroethylene resin material containing a conductive substance and a surfactant, 4 a, 4 b, 4
c: electrode, 5 a, 5 b, 5 c: electrode, 6 a, 6 b, 6 c: pure water detection sensor, 7 a,
7b, 7c: Protective layer.

Claims (1)

[Claims] 1) A pure water detection sensor characterized in that at least two electrodes are isolated by disposing a porous tetrafluoroethylene resin material containing a conductive substance and a surfactant in a portion between the electrodes.